Development of Expansive-High Strength Concrete and Systematic Evaluation of Structural Behavior of Reinforced Concrete Beams

膨胀高强混凝土的开发及钢筋混凝土梁结构性能的系统评价

基本信息

批准号：
16360220
负责人：
SATO Ryoichi
金额：
$ 8.83万
依托单位：
Hiroshima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

Expansive-high strength concrete(E-LAS) with compressive strength over 100N/mm^2 and expansive strain reaching 200 X 10^<-8> at maximum was developed, which was made of low heat Portland cement, expansive additive and shrinkage reducing agent.Stress produced in E-LAS ranged from 0.5 to・.2 N/mm2, which was not strongly dependent on the strain.The ultimate and rate of creep strains of E-LAS and conventional HSC(N-HAS) obtained experimentally showed less difference between both concretes for the case of with water to binder ratios(W/B) of 0.3. Linear creep analysis based on step by step for reinforced HSC beams showed fairly good agreement with experimental results, while the former overestimated shrinkage stress and underestimate expansive stress of HSC with W/B of 0.15 with the increase of RB ratio. The reason for the overestimate of shrinkage stress was explained by the detection of micro cracking developed in the radial direction and the computed result was improved by incorporating t … More ension softening of concrete depending on the age.Effectiveness of E-LAS was verified by experiment for improving the serviceability performance of short-and long-term flexural crack width as well as curvature of reinforced concrete(RC) beams and a new concept was proposed for evaluating them based on the strain change in tension RB from the zero concrete stress condition at tension RB depth to the loaded condition and the change of stress related curvature before and after loading, respectively, whose validity was verified by comparing with results obtained by conventional method and experiment, while tension softening effect must be considered in case of small crack width.Shear strength at diagonal cracking of E-LAS beams, whose effective depth(d) is from 250-1000mm and strain in tension RB before loading is almost zero, was improved by 5% for d=250mm, 12% for d=500mm and 19% for d=1000mm, compared with that of N-HAS beams with remarkable shrinkage strain in the same RB. A concept of equivalent tension RB ratio considering RB strain due to early age deformation was proposed. The concept showed the linear relationship between shear strength at diagonal cracking and (effective depth)^<-1/3> independent of early age deformation, while previouisly proposed equations followed the law of (effective depth)^<-1/2> and (effective depth)^<-2/5> for RC beams made of N-HAS. A proposed equation formulated based on this concept showed high prediction accuracy independent of the magnitude of early age deformation in concrete.E-LAS was also effective in improving shear strength of RC beams which was 13% for shear RB ratio of 0.25% and 6% for 0.51% higher than that of corresponding N-HAS beam, respectively. The shear RB strains averaged along a primary shear crack of E-LAS beams were smaller than those of N-HAS beams which could be roughly predicted by the modified truss theory applied a proposed equation for evaluating concrete contribution for shear resistance. Less

研制了以低热硅酸盐水泥、膨胀剂和减缩剂配制而成的抗压强度超过100N/mm^2、膨胀应变最大可达200×10^<-8>的膨胀高强度混凝土（E-LAS）。 E-LAS 产生的应力范围为 0.5 至・.2 N/mm2，对应变的依赖性并不强。E-LAS 与传统材料的蠕变应变极限和速率实验获得的 HSC(N-HAS) 表明，在水胶比 (W/B) 为 0.3 的情况下，基于增强 HSC 梁的逐步线性徐变分析表明，两种混凝土之间的差异较小。，而随着RB比的增加，前者高估了W/B为0.15的HSC的收缩应力并低估了膨胀应力。通过微裂纹的检测解释了高估收缩应力的原因。在径向方向上开发，并通过根据年龄结合混凝土的拉伸软化来改进计算结果。通过实验验证了 E-LAS 的有效性，以提高短期和长期弯曲裂缝宽度的使用性能：提出了一种评估钢筋混凝土梁曲率的新概念，该概念基于从受拉 RB 深度处的零混凝土应力条件到加载条件的受拉 RB 应变变化以及相关应力的变化分别计算加载前和加载后的曲率，与常规方法和试验结果进行比较，验证了其有效性，但在裂缝宽度较小的情况下，必须考虑拉伸软化效应。E-LAS梁斜裂时的抗剪强度，其有效值深度（d）为250-1000mm，加载前拉伸RB应变几乎为零，d=250mm时改善5%，d=500mm时改善12%与相同 RB 中收缩应变显着的 N-HAS 梁相比，d=1000mm 时为 19% 提出了考虑早期变形引起的 RB 应变的等效拉力 RB 比的概念，该概念显示了剪力之间的线性关系。对角开裂处的强度和（有效深度）^<-1/3> 与早期变形无关，而之前提出的方程遵循（有效深度）^<-1/2> 和对于由 N-HAS 制成的 RC 梁（有效深度）^<-2/5>，基于此概念提出的方程公式显示出与混凝土早期变形大小无关的高预测精度。E-LAS 在以下方面也很有效。提高了 RC 梁的抗剪强度，其 RB 比为 0.25% 时抗剪强度提高了 13%，比相应的 N-HAS 梁抗剪强度提高了 6%（0.51%）。 E-LAS 梁的主剪裂比 N-HAS 梁的小，这可以通过应用改进的桁架理论应用评估混凝土抗剪力贡献的方程来粗略预测。